Get the Length of Text Without Using Inbuild Python Library Function

In Python, the length of a string can be calculated without using any library function by iterating through the characters of the string and counting them manually. This process involves creating a counter variable and incrementing it for each character encountered in the string. In this article, we will explore four different approaches to calculating the length of a string without using the library function.

Below are some of the ways by which we can calculate the length of the string without using a library function in Python.

Using for Loop
Using lambda Function
Using enumerate Function
Using Recursion

Calculate the Length of the String Using for Loop

The below Python code defines a user-defined function lengthOfString that calculates the length of a given string using a for loop. It iterates through each character in the input string, incrementing a counter variable (length) for each character, and returns the final count as the length of the string.

Python3

# input string
string = "GeeksForGeeks"
 
# user-defined function
 
 
def lengthOfString(String):
    length = 0
    # for loop to calculate length of string
    for char in String:
        length += 1
    return length
 
 
# printing output
print("Length of the string:", lengthOfString(string))

Output

Length of the string: 13

Time complexity: O(n)
Space complexity: O(1)

Calculate the Length of the String Using lambda Function

The below Python code defines a user-defined function length_of_string that calculates the length of a given string using lambda function and mapping. We can use map and lambda to create a list of 1’s with the same length as the string and then use the sum function to add up those 1’s, giving us the length of the string.

Python3

# input string
string = "GeeksForGeeks"
 
# function defined
def length_of_string(string):
    # creating a list of 1's with the same length as the string using map and lambda
    ones_list = list(map(lambda x: 1, string))
 
    # calculating the length of the string by summing up the elements in the ones_list
    length = sum(ones_list)
    return length
 
 
# printing the length of the string
print("Length of the string:", length_of_string(string))

Output

Length of the string: 13

Space complexity: O(n)
Time complexity: O(n)

Calculate the Length of the String Using enumerate Function

The below code defines a function length_of_string_enumerate that calculates the length of the given string “GeeksforGeeks” using the enumerate function in a loop. The output is then printed, showing the length of the string as 13.

Python3

# Using enumerate
string = "GeeksforGeeks"
 
# defining function
def length_of_string_enumerate(string):
    count = 0
    # using enumerate to calculate length
    for _ in enumerate(string):
        count += 1
    return count
 
 
result = length_of_string_enumerate(string)
# printing output
print("Length of the string:", result)

Output

Length of the string: 13

Space Complexity: O(n)

Time complexity: O(1)

Calculate the Length of the String Using Recursion

The below Python code defines a user-defined function lengthOfString that calculates the length of a given string using recursion. This function returns a value that calls itself until the index has not reached its limit.

Python3

# input string
string = "GeeksForGeeks"
 
def lengthOfString(String, index=0):
    # if the current index is at the end of the string, return 0
    if not String[index:]:
        return 0
    # increment the length and call the function with the next index
    return 1 + lengthOfString(String, index + 1)
 
 
  # printing output
print("Length of the string:", lengthOfString(string))

Output

Length of the string: 13

Time Complexity: O(n)

Space complexity: O(n)

Conclusion

In conclusion, these four approaches provide different methods for calculating the length of a string in Python without using library functions. The for loop and lambda function approaches offer simplicity and efficiency, with O(n) time complexity. The enumerate function demonstrates a concise way to calculate the length with O(1) space complexity. The recursive approach, while clear in concept, comes with higher space complexity (O(n)) due to the recursive calls

Reffered: https://www.geeksforgeeks.org

Python

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